What is the most economical way to get from Huai'an to Hong Kong? Where to apply for a visa?

Following a tour group is the most economical and basically allocates one day of free time. It is not possible to apply for an individual visa in Huai'an, and if you don't apply with a tour group, it will be very troublesome and time-consuming. Which places in Nanjing and Shanghai can apply for an individual visa? If you apply for a visa and go by yourself, the round-trip fare alone is more than half of that of a group tour, and there are accommodation issues and other issues that are very annoying, so if you don’t know people in Hong Kong, you might as well go with a tour group~